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\name{rgl.surface}
\title{add height-field surface shape}
\alias{rgl.surface}
\description{
Adds a surface to the current scene. The surface is defined by
a matrix defining the height of each grid point and two vectors
defining the grid.
}
\usage{
rgl.surface(x, z, y, coords=1:3, ...,
normal_x=NULL, normal_y=NULL, normal_z=NULL,
texture_s=NULL, texture_t=NULL)
}
\arguments{
\item{ x }{
values corresponding to rows of \code{y}, or matrix of x coordinates
}
\item{ y }{
matrix of height values
}
\item{ z }{
values corresponding to columns of \code{y}, or matrix of z coordinates
}
\item{ coords }{
See details
}
\item{ ... }{Material and texture properties. See \code{\link{rgl.material}} for details.}
\item{normal_x, normal_y, normal_z}{
matrices of the same dimension as \code{y} giving the coordinates of normals at
each grid point}
\item{texture_s, texture_t}{
matrices of the same dimension as \code{z} giving the coordinates within the current texture
of each grid point}
}
\details{
Adds a surface mesh to the current scene. The surface is defined by
the matrix of height values in \code{y}, with rows corresponding
to the values in \code{x} and columns corresponding to the values in
\code{z}.
The \code{coords} parameter can be used to change the geometric
interpretation of \code{x}, \code{y}, and \code{z}. The first entry
of \code{coords} indicates which coordinate (\code{1=X},
\code{2=Y}, \code{3=Z}) corresponds to the \code{x} parameter.
Similarly the second entry corresponds to the \code{y} parameter,
and the third entry to the \code{z} parameter. In this way
surfaces may be defined over any coordinate plane.
If the normals are not supplied, they will be calculated automatically based
on neighbouring points.
Texture coordinates run from 0 to 1 over each dimension of the texture bitmap.
If texture coordinates are not supplied, they will be calculated to
render the texture exactly once over the grid. Values greater than 1 can be
used to repeat the texture over the surface.
\code{rgl.surface} always draws the surface with the `front' upwards
(i.e. towards higher \code{y} values). This can be used to render
the top and bottom differently; see \code{\link{rgl.material}} and
the example below.
If the \code{x} or \code{z} argument is a matrix, then it must be of the same
dimension as \code{y}, and the values in the matrix will be used for the corresponding
coordinates. This is used to plot shapes such as cylinders
where y is not a function of x and z.
\code{NA} values in the height matrix are not drawn.
}
\value{
The object ID of the displayed surface is returned invisibly.
}
\examples{
#
# volcano example taken from "persp"
#
data(volcano)
y <- 2 * volcano # Exaggerate the relief
x <- 10 * (1:nrow(y)) # 10 meter spacing (S to N)
z <- 10 * (1:ncol(y)) # 10 meter spacing (E to W)
ylim <- range(y)
ylen <- ylim[2] - ylim[1] + 1
colorlut <- terrain.colors(ylen) # height color lookup table
col <- colorlut[ y-ylim[1]+1 ] # assign colors to heights for each point
rgl.open()
rgl.surface(x, z, y, color=col, back="lines")
}
\seealso{
\code{\link{rgl.material}}, \code{\link{surface3d}}, \code{\link{terrain3d}}.
See \code{\link{persp3d}} for a higher level interface.
}
\keyword{dynamic}
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